131 lines
4.9 KiB
C
131 lines
4.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* dshash.h
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* Concurrent hash tables backed by dynamic shared memory areas.
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/include/lib/dshash.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef DSHASH_H
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#define DSHASH_H
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#include "utils/dsa.h"
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/* The opaque type representing a hash table. */
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struct dshash_table;
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typedef struct dshash_table dshash_table;
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/* A handle for a dshash_table which can be shared with other processes. */
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typedef dsa_pointer dshash_table_handle;
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/* Sentinel value to use for invalid dshash_table handles. */
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#define DSHASH_HANDLE_INVALID ((dshash_table_handle) InvalidDsaPointer)
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/* The type for hash values. */
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typedef uint32 dshash_hash;
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/* A function type for comparing keys. */
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typedef int (*dshash_compare_function) (const void *a, const void *b,
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size_t size, void *arg);
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/* A function type for computing hash values for keys. */
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typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size,
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void *arg);
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/* A function type for copying keys. */
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typedef void (*dshash_copy_function) (void *dest, const void *src, size_t size,
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void *arg);
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/*
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* The set of parameters needed to create or attach to a hash table. The
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* tranche_id member does not need to be initialized when attaching to an
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* existing hash table.
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*
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* Compare, hash, and copy functions must be supplied even when attaching,
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* because we can't safely share function pointers between backends in general.
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* The user data pointer supplied to the create and attach functions will be
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* passed to these functions.
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*/
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typedef struct dshash_parameters
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{
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size_t key_size; /* Size of the key (initial bytes of entry) */
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size_t entry_size; /* Total size of entry */
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dshash_compare_function compare_function; /* Compare function */
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dshash_hash_function hash_function; /* Hash function */
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dshash_copy_function copy_function; /* Copy function */
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int tranche_id; /* The tranche ID to use for locks */
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} dshash_parameters;
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/* Forward declaration of private types for use only by dshash.c. */
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struct dshash_table_item;
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typedef struct dshash_table_item dshash_table_item;
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/*
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* Sequential scan state. The detail is exposed to let users know the storage
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* size but it should be considered as an opaque type by callers.
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*/
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typedef struct dshash_seq_status
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{
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dshash_table *hash_table; /* dshash table working on */
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int curbucket; /* bucket number we are at */
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int nbuckets; /* total number of buckets in the dshash */
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dshash_table_item *curitem; /* item we are currently at */
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dsa_pointer pnextitem; /* dsa-pointer to the next item */
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int curpartition; /* partition number we are at */
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bool exclusive; /* locking mode */
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} dshash_seq_status;
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/* Creating, sharing and destroying from hash tables. */
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extern dshash_table *dshash_create(dsa_area *area,
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const dshash_parameters *params,
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void *arg);
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extern dshash_table *dshash_attach(dsa_area *area,
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const dshash_parameters *params,
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dshash_table_handle handle,
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void *arg);
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extern void dshash_detach(dshash_table *hash_table);
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extern dshash_table_handle dshash_get_hash_table_handle(dshash_table *hash_table);
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extern void dshash_destroy(dshash_table *hash_table);
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/* Finding, creating, deleting entries. */
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extern void *dshash_find(dshash_table *hash_table,
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const void *key, bool exclusive);
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extern void *dshash_find_or_insert(dshash_table *hash_table,
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const void *key, bool *found);
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extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
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extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
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extern void dshash_release_lock(dshash_table *hash_table, void *entry);
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/* seq scan support */
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extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table,
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bool exclusive);
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extern void *dshash_seq_next(dshash_seq_status *status);
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extern void dshash_seq_term(dshash_seq_status *status);
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extern void dshash_delete_current(dshash_seq_status *status);
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/*
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* Convenience hash, compare, and copy functions wrapping memcmp, tag_hash, and
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* memcpy.
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*/
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extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg);
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extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg);
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extern void dshash_memcpy(void *dest, const void *src, size_t size, void *arg);
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/*
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* Convenience hash, compare, and copy functions wrapping strcmp, string_hash,
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* and strcpy.
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*/
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extern int dshash_strcmp(const void *a, const void *b, size_t size, void *arg);
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extern dshash_hash dshash_strhash(const void *v, size_t size, void *arg);
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extern void dshash_strcpy(void *dest, const void *src, size_t size, void *arg);
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/* Debugging support. */
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extern void dshash_dump(dshash_table *hash_table);
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#endif /* DSHASH_H */
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